Comparative Study Of Cold Acclimation And Deacclimation In Three Floribunda Roses Varieties

Floribunda roses(Rosa hybrida ‘Floribunda’) are evergreen or semi-evergreen low shrubs of Rosaceae, Rosa L. The floribunda roses have a lot of varieties, robust growth momentum and strong resistance. The floribunda roses are widely used in landscaping currently. From September 2013 to May 2014, the three floribunda roses varieties: ‘Hongcongrong’, ‘Rouqingsishui’, and ‘Xianjing’ were used monthly to measure the frost hardiness(FH) by means of the methods of direct field observation, electrolyte leakage(EL) and electrical impedance spectroscopy(EIS)(re), and the non-frost-exposed EIS parameters and the content of soluble sugar and starch in stems and leaves. The FH measured by EL and EIS(re) was compared. The relations between non-frost-exposed EIS parameters and FH, between non-frost-exposed EIS parameters and the content of soluble sugar and starch, and between the content of soluble sugar and starch and FH measured by EIS(re) were analyzed. Subordinate function was applied to assess comprehensively the FH of the three floribunda roses varieties.The main results are as follows:1. During cold acclimation and deacclimation, the order of FH measured by EL and EIS(re) for stems of floribunda roses varieties was ‘Xianjing’ > ‘Rouqingsishui’ > ‘Hongcongrong’. The order of FH for leaves of floribunda roses varieties was ‘Rouqingsishui’ > ‘Xianjing’ > ‘Hongcongrong’. According to the subordinate function of cold resistance indicator, the order of FH for stems of floribunda roses varieties was ‘Rouqingsishui’ > ‘Xianjing’ > ‘Hongcongrong’. The order of FH for leaves of floribunda roses varieties was ‘Rouqingsishui’ > ‘Hongcongrong’ > ‘Xianjing’ in November, December and April, ‘Xianjing’ > ‘Rouqingsishui’ > ‘Hongcongrong’ in September, March and May, and ‘Hongcongrong’ > ‘Xianjing’ > ‘Rouqingsishui’ in October.2. Some EIS parameters in non-frost-exposed stems and leaves correlated highly with the FH measured by EL. The changes of the EIS parameters can effectively reflect the internal changes of plant under the chilling stress. Therefore the EIS parameters can be used to estimate the FH in stems and leaves of the three floribunda roses varieties.3. The FH of stems and leaves of the three floribunda roses varieties measured by EL and EIS(re) methods presented similar tendency. However, the degree of FH estimated by the EIS method was lower than that by the EL method.4. There was a certain correlation between the EIS parameters(specific extracellular resistance re, specific intracellular resistance ri and distribution coefficient of relaxation time ψ) in non-frost-exposed and the content of soluble sugar and starch.5. The FH measured by EIS(re) for stems of floribunda roses varieties had a high correlation with the content of soluble sugar and starch(R2=0.82~0.99). There were positive relations between soluble sugar content and the FH measured by EIS(re). There were negative relations between starch content and the FH measured by EIS(re). The FH measured by EIS(re) for leaves had a high correlation with the content of soluble sugar(R2=0.82~0.99), but a low correlation with the content of starch.